Helmet liner



FIG. 1 is a bottom perspective view of a helmet liner showing our new design;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a side elevation view thereof, wherein the left side, right side, front and rear views are identical; and,

FIG. 4 is a top plan view thereof.

The broken lines shown in the drawings are for illustrative purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a helmet liner, as shown and described. 